It is recognized in the art that the non-variable nature of valve duration in the internal combustion engine is a serious impediment to optimal efficiency. The varying dynamics of an engine having optimal efficiency throughout the range of it's operation would demand continuous adjustments in the duration relative to crankshaft revolution, of the processes of induction and exhaust.
The benefits of such a system would be considerable improvements in the areas of economy, reduced emmission levels and increased power. The benefits to torque characteristics of such an engine would allow smaller engines for given vehicle weight; the weight saving so achieved improving overall vehicle efficiency still further.
In view of these facts, many attempts have been made to provide a mechanism capable of giving at least some of the above benefits.
The difficulties in producing such inventions lie, not in designing reliable mechanisms to bodily re-index a camshaft relative to crankshaft revolution, since one or two such systems are in production--Mercedes and Toyota, for example--but are capable of achieving only a minor effect since a simple reindexing of the camshaft cannot provide a variation in the duration of an induction or exhaust process.
Accordingly, attempts have been made, for instance, to apply the aforesaid principle of re-indexing to a pair of camlobes operating a single valve, with mechanisms that attempt to combine the motion of the opening flank of a first camlobe with the motion of the closing flank of a second camlobe, and by variably indexing the two camlobes relative to each other, producing a variation in the duration of the valve.
Results stemming from this approach illustrate the extreme difficulty in combining the disparate motions generated by two camlobes differentially phased into a single motion of use in this context. FIG. 11 of the drawings depicts a sample of this dynamically unacceptable valve motion.
Accordingly, a system is proposed by the inventor that provides continuously variable duration of the exhaust and induction processes, without altering the duration of the valves associated with such processes, and without departing from the dynamics of camlobe/valve relationships that are proven in all engines having conventional non-variable valve train systems. The aforesaid system requiring, in part, the use of two camshafts, and a mechanism to variably re-index these camshafts relative to each other, and relative to crankshaft revolution, prior art camshaft variable indexing mechanisms are referenced, for example, such as GARCEA November 4, 1980, U.S. Pat. No. 4,231,330, and AKASAKA et al Mar. 14, 1989, U.S. Patent No. 4,811,698, it being noted that both devices offer only the capability of angularly re-indexing a single camshaft.